Do take time to read the forum library and read various adSense optimization tips and strategies. Do also read the official help on Google adSense. Everything you need is available on this site and on G adSense site.

BTW welcome to WW.

You don't have to register each website with Google. You can paste the same code on all of your pages, but I would advise that you use the channels facility, giving each blog a separate identity. That way you can track the performance of each blog.

I would encourage you to read the Google terms and conditions, and general guidelines they give on the adsense site to ensure that your pages meet Google's requirements. If they don't there is the danger that you will lose your account

can i use this same code on rest of my blogs or do i have to register to google adsense again and getting new code and adding on next one blog?

yes, use single adsense account for all your blogs(shud satisfy adsense tos and prog policies). no need to register again and again.

what are other online money making strategies? like google adsense.

try adbrite, textlinkads for blogs.